Combined propylene carbonate and aromatic hydrocarbon solution of a vinyl resin



United States Patent CQMBINED PRGPYLENE CARTBQNA'IE AND AROMATIC HYDROCARBON SOLUTION OF A VINYL RESIN Gerald P. Rees er, Laliaska, Pa., assignor, by mesne assignments, to American-Marietta Company, Stoner- Mudge 0. Division, Chicago, 111., a corporation of Illinois No Drawing. Application-August 31, 1956 Serial No. 607,287 I 7 Claims. ((11. 26030.4)

This invention relates to the use of propylene carbonate in conjunction with aromatic hydrocarbon solvents to dissolve certain resins, especially copolymers of vinyl chloride and vinyl acetate.

Vinyl polymers and copolymers have become well known in many industries for their valuable properties, and one phase of their development has been a search for suitable solvents to form solutions of the polymers for various purposes, such as protective coatings, films, and various other plastic applications. There are a number of active solvents which have been found to be generally suitable for such purposes, such as isop'horone, cyclohexanone and methyl ethyl ketone. Such active solvents are expensive, however, and consequently attempts have been made to find less expensive substitutes. The common aromatic hydrocarbon solvents are much less expensive, but they can be used only as diluents with more active solvents to dissolve most vinyl polymers and copolymers, with rare exceptions; e. g., straight aromatic hydrocarbon solvents with vinyl chloride/vinylidene chloride copolymers as disclosed in Gray and Reymann U. S. Patent 2,675,334. In the case of copolymers of vinyl chloride and vinyl acetate, which are among the most widely accepted and useful of the vinyl compounds, particularly in the protective coating field, it is necessary to use expensive active solvents, either exclusively or in relatively large proportions with aromatic hydrocarbon solvents, in order to dissolve the vinyl chloride/vinyl acetate copolymers sufiiciently to obtain the desired viscosity. The resultant expense and other difiiculties have led to a long continued search for other solvent materials which could be used in smaller proportions with aromatic hydrocarbon solvents for obtaining suitable solutions of vinyl chloride/vinyl acetate copolymers.

I have discovered that there is a synergistic relation between propylene carbonate and liquid aromatic hydrocarbons such as benzene, toluene and xylene, and mixtures thereof, whereby the combination of the two is highly efiective when used with certain resins, particularly copolymers of vinyl chloride and vinyl acetate containing less than 90% by weight of vinyl chloride. The structural formula of propylene carbonate may be expressed as follows:

H La

There is evidently a special relation between the propylene carbonate component of the solvent system and the aromatic hydrocarbon component, because neither one of the components used alone is capable of dissolving these resins, but the combination of the two components is highly efiective in dissolving them. The combination is particularly valuable because of its usefulness as a solvent for vinyl chloride/vinyl acetate copolymers, which are of major commercial importance, and because ice a very high percentage of the aromatic hydrocarbon component, which is relatively inexpensive, can be used in the solvent mixture for purposes of dissolving vinyl chloride/vinyl acetate copolymers, in spite of the fact that such copolymers are noted for their resistance to dissolution in conventional solvent mixtures containing like percentages of such aromatic hydrocarbon component.

The solvent composition of the invention consists of the combination of propylene carbonate with benzene, toluene or xylene, or mixtures thereof. When used as a solvent for copolymers of vinyl chloride and vinyl acetate containing about 87% by weight of vinyl chloride, the composition of the invention is efiective in a range of proportions of propylene carbonate of about 9% to about by weight (the balance being benzene, toluene, or xylene, or mixtures thereof). As the proportion of vinyl chloride in the copolymer is decreased below 87% the greater solvency of the vinyl acetate in the copolymer makes the composition of the invention effective as a solvent for the copolymer with a progressively smaller minimum and larger maximum proportion of propylene carbonate.

The following Table I shows the effectiveness of propylene carbonate as compared with cyclohexanone and isophorone when'used in various proportions with xylene, in terms of viscosities (in seconds at F. with #4 Ford cup) of compositions consisting of uniform samples of vinyl chloride/vinyl acetate copolymer (87/13 ratio, VYI-Il-I) at 18% solids by weight in the various solvent mixtures (component ratios by weight):

TABLE I.COb IPARATIVE VISCOSITIES [Seconds at 80 F. with a i Ford cup] viscosities of 18% solids VYHH in the following solvent combinations Ratios of solvent compone)nt(s3n col. headings (1), (l) (2) (3) Oyclohexa- Isophorone Propylene none and and xylene carbonate xylene and xylene Swollen.

Do. 155. 67. 50. 4.7. 52. 87. 94. Swollen.

Do. Do. Insol.

TABLE II.-COMPARATIVE VISGOSITIES VV'HEN USING PROPYLENE CARBONATE WITH DIFFERENT AROLIAT- IC HYDROCARBQNS [Seconds at 80 F. with a #4 Ford cup] viscosities of 18% solids VYHH in Ratio of propylene I combinations of propylene carbonate withcarbonate to the aromatic hydrocarbon specified in adjacent headings Benzene Toluene Xylene SolVesso (by weight) #IUU Swollen... Swollen... Swollen." Swollen. 14 15' 178.

88. Gel. Insol.

I "EXON 405 1 In the above Table H, Solvesso #100 (Esso Stand-- vinyl resins, in terms of comparative viscosities .(in secjondsat 80 F. with #4 Ford'cup) when-using propylene carbonate and xylene separately and in various combined proportions with the resins:-

. TABLE III...C.O1\IPARATIVE VISOOSITIES WITH DIFFERENT RESIN'S V I [Seconds at 80 F. with a #4 Ford cup.]

Pnrnent Ratio propylene carbonate/xylene (by weight) solids Resin Geon 200 1111015 above Table III, and (Union Carbide and Carbon Corporation, New York, N. 'Y.) are copolymers of vinyl'chloride and vinyl acetate in proportions of 87/13 by weight, the difference between the two lying in the fact that 'VYHH has a higher molecu-' lar weight. VMCH .(Union Carbide and Carbon Corp.) is a copolymer of vinyl chloride, vinyl acetate and maleic anhydride, in proportions by weight of 86/ 13/ 1. VAGH (Union Carbide and Carbon Corp.) is a partially hydrolyzed copolymer of vinyl chloride and vinyl acetate, the copolymer being originally like VYHH, but changed by hydrolysis to proportions by weight of 6% vinyl" alcohol, 3% vinyl. acetate and 91% vinyl chloride. V YNS (Union Carbide and Carbon Corp.) is a copolymer of vinyl chloride and vinyl acetate in proportions by weight. of 90/10. QYNV (Union Carbide and Carbon Corp.) and Exon 402 (Firestone Plastics Co., Pottstown, Pennsylvania),. are polymers consisting entirely'of polyvinyl chloride, and Geon 200x20? (B. F. Goodrich Chemical Co., Cleveland, Ohio), is a copolymer of vinylchloride and vinylidinechloride.

The mixed solvent of the invention is efiective with copolymers of vinyl chloride and vinyl acetate containing less than 90% by weight ofvinyl chloride. There is no upper limit on the amount of vinyl acetate in the copolymer because the vinyl acetatecomponent is relatively easily dissolved, For example, 100% vinyl acetate polymer is soluble in all mixtures of propylene carbonate and xylene containing about 9% to about 75% by weight of propylene carbonate, the balance being xylene. '7

Compositions employing the polymer and solvent coma bination of the invention are useful for protective coating and other purposes for which vinyl chloride/vinyl acetate solutions are used. For example, a compositionof the above-described VYHH vinyl chloride/vinyl acetate copolymer at 18% applied solids in solvent consisting of 67%xylene and 33% propylene carbonate was filmed on tinplate at about 4.7 mg./ sq. in. and baked thereon at When commercial naphstated above.

about 335 F. for ten minutes. The coating was tested for color, clarity, flow, adhesion, insolubility, flexibility,

and, after pasteurization at 170 F. for 45 minutes, for blistering, spotting and wet adhesion. For purposes of comparsion, a composition ofthe same copolymer at.

19.5% applied solids in solvent consisting of67% toluene and 33%. methyl ethyl ketone was filmed on like specimens at 5'.3jmg./sq. in. and thenbaked and tested as The results were essentially the same in b h. QSShOWin'g-that coating qualities-are not adversely afiected -by substitution of propylene carbonate for such standard solvents as methyl ethyl ketone in coat ing compositions of vinyl chloride/vinyl acetate copolymers. The composition of the invention can have a viscosity range of 20m 150 seconds in #4 Ford cup at 80, F., and a solidsconcentration of vinyl chloride/vinyl acetate copolymerof up to about 21% by weight, ifOI' copolymer of vinyl chloride and vinyl acetate contains most protective coating purposes,but these ranges can be exceeded for some protective coating purposes.

Pigments, dyes, waxes and other'non-reactants may be added to the composition of the invention for'de'corative purposes and the like,'without otherwise materially afiecting the significant characteristics of the composition. a 7 While I have described present preferred embodiments of the invention and methods of practicing the same,.it

will be recognized thatthe invention is not limited therev to but maybe otherwise variously'embodied andpracticed within the scope ofthe following claims.

I claim: A

1. A'resin solution comprising a copolymer of-vinyl chloride andvinyl acetate containing less than 90% by weight of vinylchloride in said copolymer, said copolymer being dissolved in a solvent medium consisting essentially of an aromatic hydrocarbon selected from the group consistingvofbenzene, toluene, xylene, and mixtures thereof, and propylenecarbonate, said mixture containing from 9% -to about by weight of propylene carbonate based on the combined weightof said propylene 'carbonate andaromatic hydrocarbon. 3

2. A resinsolution as recited in claim 1' in whichsaid not more than about 87% by weight of vinyl chloride.

3. A resinsolution as recited in claim 1 in'which said aromatic hydrocarbon is xylene.

4; A resinsolution as recited in claim 1 in which said copolymer of vinyl chloride and vinyl acetate contains substantially 87% by weight of vinyl chloride.

' '5. A resin solution as recited-in claim 4 in which said propylene carbonate is present inan amount of about 9% by weight. V V

6. A resinsolution comprising a copolymer of vinyl chloride-and vinyl acetate containing less than 90% by weight of vinyl chloride in said copolymer, said copolymer being dissolved in a solvent medium consisting essentially of an aromatic hydrocarbon selected from the group consisting of benzene, toluene, xylene and mixtures-thereof, and propylene carbonate, said mixture containing from 25% to 50%" by weight of propylene carbonate based References Cited in the file of this patent UNITED STATES PATENTS 2,764,469 Kowolik etal. Sept. 25, 1956 1,769,792 Ham Nov. 6, 1956' 

1. A RESIN SOLUTION COMPRISING A COPOLYMER OF VINYL CHLORIDE AND VINYL ACETATE CONTAINING LESS THAN 90% BY WEIGHT OF VINYL CHLORIDE IN SAID COPOLYMER, SAID COPOLYMER BEING DISSOVED IN A SOLVENT MEDIUM CONSISTING ESSENTIALLY OF AN AROMATIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE, TOLUENE, XYLENE, AND MIXTURES THEREOF, AND PROPULENE CARBONATE, SAID MIXTURE CONTAINING FROM 9% TO ABOUT 75% BY WEIGHT OF PROPYLENE CARBONATE BASED ON THE COMBINED WEIGHT OF SAID PROPYLENE CARBONATE AND AROMATIC HYDROCARBON. 